Semiconductor optical amplifier pulse reshaper

Abstract

A system includes a pulse reshaper for reshaping and re-amplifying optical signals in a communications network. In one embodiment, a vertical cavity semiconductor optical amplifier (VCSOA) device, comprising dual mode reflectors optically cooperating at each of an input signal wavelength (λ s ) and an offset wavelength (λ c ) proximate the input signal wavelength (λ s ) to provide thereby non-linear amplification of input signal (λ s ).

1. A vertical cavity semiconductor optical amplifier (VCSOA), comprising:
 dual mode reflectors having respective first reflective portions defining a first mode and respective second reflective portions defining a second mode, the second reflective portions being inside a region defined by the first reflective portions; 
 wherein the dual mode reflectors are configured for providing an output having a first wavelength (λs) and an offset wavelength (λc) proximate the first wavelength (λs), the first and second reflective portions having higher reflectivities at the offset wavelength (λc) than at the first wavelength (λs) for implementing non-linear amplification of an input signal at the first wavelength (λs) by competition between the first and second modes. 
 
     
     
       2. The SOA of  claim 1 , wherein the SOA is an in-plane SOA using a distributed feedback (DFB) layer comprising first and second reflective regions to implement dual mode operation of the SOA. 
     
     
       3. The VCSOA of  claim 1 , wherein the dual mode reflectors are distributed Bragg reflectors (DBRs). 
     
     
       4. The VCSOA of  claim 3 , wherein one of two modes of the dual mode VCSOA clamps the gain of the VCSOA, wherein an active medium layer works in deep saturation condition. 
     
     
       5. The VCSOA of  claim 1 , wherein the input signal wavelength is greater than the offset wavelength. 
     
     
       6. The VCSOA of  claim 5 , wherein interaction between the offset wavelength and input signal wavelength within the cavity of the VCSOA results in a non-linear amplification of input signal (λs). 
     
     
       7. The VCSOA of  claim 1 , wherein the offset wavelength is approximately within 0.4 nm of the input signal wavelength (λs). 
     
     
       8. The VCSOA of  claim 1 , wherein if λs has signal intensity below a threshold, then the VCSOA lases at the offset wavelength λc. 
     
     
       9. The VCSOA of  claim 1 , wherein if λs has signal intensity above a threshold, then the VCSOA amplifies the input signal λs and the offset wavelength is suppressed by the signal mode at the output of the VCSOA. 
     
     
       10. The VCSOA of  claim 1 , further comprises a pump, wherein the pump has a pumping level above clamp mode lasing threshold and under signal lasing threshold. 
     
     
       11. The VCSOA of  claim 1 , wherein the offset wavelength is of a range between −0.4 nm and +4.0nm of the input signal wavelength (λs). 
     
     
       12. The VCSOA of  claim 1 , wherein the first reflective portions and the second reflective portions are each characterized by respective effective cavity lengths, each of the effective cavity lengths being given by an equation: L=nλ/2, where n is an integer; and the equation is satisfied for wavelength λ at both the first wavelength (λs) and the offset wavelength (λc). 
     
     
       13. The VCSOA of  claim 1 , wherein the difference between the first wavelength (λs) and the offset wavelength (λc) is varied by adjusting at least an effective cavity length for the mode associated with the offset wavelength. 
     
     
       14. A method of operating a vertical cavity semiconductor optical amplifier (VCSOA), comprising:
 providing dual mode reflectors having respective first reflective portions defining a first mode and respective second reflective portions defining a second mode, the second reflective portions being inside a region defined by the first reflective portions; configuring the dual mode reflectors for providing an output having a first wavelength (λs) and an offset wavelength (λc) proximate the first wavelength (λs); 
 wherein the first and second reflective portions have higher reflectivities at the offset wavelength (λc) than at the first wavelength (λs); and 
 wherein the first reflective portions and the second reflective portions are each characterized by respective effective cavity lengths, each of the effective cavity lengths being given by an equation: L=nλ/2, where n is an integer; and the equation is satisfied for wavelength λ at both the first wavelength (λs) and the offset wavelength (λc). 
 
     
     
       15. The method of  claim 14 , further comprising:
 configuring the dual mode reflectors for competition between the first and second modes to provide a non-linear gain profile over intensity of an input signal at the first wavelength (λs) corresponding to signal logic “0” and logic “1”. 
 
     
     
       16. The method of  claim 15 , further comprising: adjusting an intensity threshold for transition between the signal logic “0” and logic “1” by varying the reflectivities of the first and second reflective portions for the two modes associated with the first wavelength (λs) and the offset wavelength (λc) and a pump level for the VCSOA.